The invention relates to a valve comprising a casing incorporating a reception space which is subdivided by a diaphragm into a first control-side chamber which may be coupled to a control pressure via a first connector, and a second, fluid-side, chamber which may be connected to a pressurised fluid via at least one second connector, and wherein a valve needle connected to the diaphragm is displaceable with respect to its seat as a function of the control pressure, in such a way that an outlet of the second chamber is closed or opened, the diaphragm being preloaded towards the closed position of the needle by means of a spring.